题解 | #自守数#

from ast import Num
import sys

def do(num):
    result = []
    # 平方
    for n in range(num+1):
        n_square = n * n
        # 截尾数
        n_len = len(str(n))
        n_square_tail = str(n_square)[-n_len:]
        n_square_tail = int(n_square_tail)
    # 比较
        if n == n_square_tail:
            result.append(n)
    return len(result)


if __name__ == '__main__':
    num = int(sys.stdin.readline())
    r = do(num)
    print(r)